The structure of the thin films of P xSe 1−x deposited at various angles incidence and the photostructural changes occuring therein on illumination with UV light been studied by infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). IR spectra reveal the absorption bands due P=Se, PSeP, and SeSe group variations. The coexistence of various types of structural units (SePSe 3 2 , PSw 3 2 and SeSe) in these films supported by XPS and IR results. The photostructural changes are a consequence of the changes in the relative concentration of these structural units. It has been shown that the magnitude of the photostructural changes is maximum for the composition (P 4Se 10) having maximum concentration of fourfold coordinated (SePSe 3 2 ) units.